Because of the nature of the improvements herein contemplated, a statement describing the major known prior art bows will be helpful. For this purpose certain of those prior art bows are also illustrated in the drawings, i.e., in FIGS. 1a to 4b inclusive, which Figures are briefly described, as follows:
FIGS. 1a and 1b are views of an ancient known oriental bow, FIG. 1a showing the bow without its string and FIG. 1b showing the bow with the string applied;
FIGS. 2a and 2b are views of the well known midieval long bow, FIG. 2a showing the bow without its string and FIG. 2b showing the bow with the string applied;
FIGS. 3a and 3b are views of a recurved hunting bow, FIG. 3a showing the bow without the string and FIG. 3b showing the bow with the string applied; and
FIGS. 4a and 4b are views of a currently used target bow, FIG. 4a showing the bow without its string and FIG. 4b showing the bow with the string applied.
The foregoing prior art bows may briefly be described as follows:
The oriental bow of FIGS. 1a and 1b was made of a wood-cored sandwich of parallel sinew fibers laminated on the tension back, and horn laminated on the compression belly. This provided an easy to handle, very short (40 inches or less) bow which had inherently fast string return and excellent efficiency, capable of an 800 yard cast. An important factor contributing to the bow efficiency is the recurved or bending backward of the limb ends which results in shortening of the bow string as it is released, thereby increasing the arrow speed. This bow had nonworking recurves, and the extent of recurvatuve as measured between the string line and the axis of each bow limb was about 30.degree. to 40.degree.. A typical 30.degree. recurve being shown in FIG. 1b.
It is here noted that in FIG. 1b and in all cases shown and described in this application, the angular extent of recurvature is given with the bow in strung condition.
The bow of FIGS. 1a and 1b was subject to various disadvantages including the fact that in order to avoid even slight twisting of the bow limbs (which invariably) destroys the bow limbs) they were made very rigid and non-working, i.e., they did not flex in use. This rigidity resulted in excessive shock in the bow handle and thus to the archer. Moreover the horn and sinew construction was highly sensitive to temperature and humidity changes.
Although the midieval long bow of FIGS. 2a and 2b was easily produced from abundant materials, i.e., selected woods, and was an easy to shoot weapon, it was, nevertheless, of relatively low efficiency and was unwieldy (about 6 feet) in order to withstand breaking stresses. The limbs had no recurvature and the bow was also sensitive to temperature and humidity changes.
The more modern bows shown in FIGS. 3a and 3b and 4a and 4b are commonly made of a wood core-glass fiber reinforced plastic sandwich. The recurved hunting bow of FIGS. 3a and 3b was rather short, i.e., from about 48 to 60 inches. These are efficient hunting weapons almost unaffected by environmental changes. The materials available for construction, allow the use of moderately (for instance approaching 45.degree.) recurved limbs of some flexibility so that they are in effect "semi-working". Some shock to the archer remains in the curved hunting bows, but this is not a serious problem to a hunter who shoots relatively seldom.
The modern target bow of FIGS. 4a and 4b combines the short semi-working recurved light weight limbs of the hunting bow with a heavy, elongated handle section, this results in a longer bow (60 to 72 inches) and the heavy handle helps to absorb most of the shock, so that tournament archers may shoot frequently without excessive fatigue. In addition it is known with target bows to add certain weights or stabilizer rods positioned to further absorb vibration. The design of the target bow, however, is such that it is heavy and unwieldy so that it is difficult to hold up at arms length for extended periods of time.
Although the use of recurved limbs is advantageous in increasing the efficiency of the bow, the recurved limbs tend to twist, particularly if the recurve is of substantial magnitude. In view of this, the recurve heretofore employed has been distinctly limited (for instance to about 25.degree. as indicated in FIG. 4b), and bows with recurved limbs have frequently been subject to highly undesirable twisting, in many instances even resulting in destruction of the bow limb.
It is a principal objective of the present invention to provide a bow having limbs which are highly recurved, but in which the tendency to twist is extensively diminished. This is accomplished by utilization of certain materials in the fabrication of the bow limbs having greater elongation and lower Young's modulus of elasticity, than the materials heretofore commonly utilized in archery bows. At the same time the bow limbs are increased in thickness thereby extensively increasing the twist resistance so that the limbs may be highly recurved without developing appreciable twisting tendency.
A further object of the invention is to provide elevated string guides mounted on the recurved limbs and arranged to further assist in overcoming the tendency of recurved limbs to twist. Such elevated string guides may be employed to advantage upon recurved limbs of any degree of recurvature, but they are particularly advantageous with highly recurved limbs of the kind contemplated according to the present invention.
A still further objective of the invention is to provide a bow construction in which the recurved limbs are separately formed and mounted upon the handle section of the bow. Provision is thus made for convenient fabrication of the bow limbs and of the handle section respectively from materials having different characteristics.
In accordance with another aspect of the invention, provision is made for adjustably mounting the separately formed bow limbs, thereby providing for adjustment of the characteristics of the bow.